Obturation caps of the above mentioned types have already been disclosed. In this connection, reference can be made to U.S. Pat. No. 5,222,530 of 1993 and to its European counterpart EP-0,641,713-B1 of 1997, both issued in the name of ELKAY MANUFACTURING CO. with designation of Henry E. BAKER et al as inventors.
Obturation caps of this type are extremely interesting but are presently difficult to manufacture in one single injection, without having to proceed to an ultrasonic welding or another type of welding. In this connection, reference can be made to the comments made in the preamble of U.S. Pat. No. 5,392,939 of 1995 in the name of Walter E. HIDDING et al where, in column 2, lines 3 to 20, mention is made to the problem of molding the cap disclosed in U.S. Pat. No. 5,121,778 of 1992 to ELKAY MANUFACTURING CO. which derives from the same parent application as U.S. Pat. No. 5,222,530 mentioned hereinabove and where, in the same column, mention is also made to the fact that it is impossible to manufacture such a cap by injection in one single piece.
International patent application No. WO 02/060808 A1 published in 2002 in the name of W. KRASKA discloses an obturation cap of the same type as mentioned hereinabove, as well as a method for manufacturing this cap by injection in one single piece. However, the potential problem with the method proposed in this international patent application is that one cannot necessarily obtain all the requested angulations and a consistence of the frangible connection. Once cannot also obtain necessarily all the requested curves to ensure that the sleeve of the cap be provided with one or more internal sealing tongues and the upper edge of this sleeve be inclined or bevelled to facilitate engagement of the plug within the sleeve during extraction of the liquid dispenser. However, these structural characteristics are actually essential when one wants to obtain a cap that is water tight and air tight and thus perfectly hygienic, in addition of having it also with tamper proof properties.